Saturable reactor



Aug. 30, 1955 H. B. REX

SATURABLE REACTOR Filed Deo. 8, 1949 R m W.. In on B. w 0 M H 6) 07CATTORNEY.;

United States Patent O SATURABLE REACTOR Harold B. Rex, Falls Church,Va.

Application December 8, 1949, Serial No. 131,882

1 Claim. (Cl. 336-155) (Granted under Title 35, U. S. Code (1952), sec.266) This invention relates to a new and improved variable reactance andparticularly to the core construction for toroidal variable reactances.

With the advent of new and improved magnetic materials of highpermeability e. g., the ferrites disclosed and claimed in the U. S.patents to Jacob L. Snoek, 2,452,529 and 2,452,530, the toroidal coilhas become of N particular advantage as a reactance element. However, ithas been impracticable in the past to utilize a toroidal coil ininstances where the inductance of the coil must be varied, because theonly practicable means for changing the inductance, and the associatedinductive reactance of the coil, was to change the actual number ofturns in the windings. In complex circuitry such as that associated withfire control equipment, wherein the coil of this invention isparticularly well adapted, it is not often feasible to permit a changein the actual number of turns in the windings.

The present invention has for its object therefore the construction of atoroidal inductance unit wherein the inductive reactance may be variablewithout altering the number of turns. It is also an object of thisinvention to provide a novel core construction for a saturable reactor.

The features of this invention by means of which the above objects areobtained reside in the use of a circumferentially wound saturatingwinding positioned within the core interior so that the saturating linesof iiuX flow through the core material in a direction normal to the pathof the main flux. Thus by altering the magnitude of the direct currentflowing in the saturating Winding the reluctance of the core material isaltered thereby altering the magnitude of the magnetic fluX produced bythe toroidal coil wound about said core in a direction generallyparalleling the direction of the saturating flux.

A better understanding of the invention may be had from the followingdescription together with the accompanying drawing in which:

Fig. l shows an isometric view partially in cross section of the overalltoroidal inductance unit of the present invention;

Fig. 2 is a partial sectional view of a modied construction of the coilcore of this invention.

Fig. 3 is a partial sectional view of a further modificatlon.

In Fig. l a toroidal coil 1 is shown wound upon a sectionalized hollowcore 2 comprised of cooperating portions 3 and 4 which are providedrespectively with circumferentially extending recesses S and 6. Theserecesses are shown as being of substantially equal rectangularcrosssection and equally positioned radially from the axis of the toroidso that when the two portions are assembled with the recessed surfacesopposing a totally enclosed space will be provided. As shown in Fig. lthe cooperating core portions are provided with slots 7 and 8 configuredso as to receive opposite ends 11 and 12 of strip wound coil 10. It willbe understood that the windings 10 include suitable insulating material,such as varnish or impregice nated paper between layers of turns. In theevent the core portions 3 and 4 are formed of ferrite as is preferred,insulation covering on the inner and outer surfaces of the strip winding10 are not required for the preferred type ferrites such as disclosed bythe above-mentioned patents to Snoek have a specific resistance greaterthan 1000 ohm-cm. rendering the core substantially nonconducting withrespect to coil 10. The ends 11 and 12 are in elfect leads or terminalsconnecting respective ends of the windingr by means of which a suitableD. C. potential may be applied to give the core 2 and coil 10 thedesired degree of transverse saturation with magnetic linx. The stripwinding 10 when formed of magnetic and electrically conductive material,such as any one of the numerous ferrous alloys known to the reactor art,as is preferred reduces the overall reluctance of the core structure.

ln the modification illustrated by Fig. 2 wherein like referencenumerals refer to like parts in the embodiment illustrated in Figs. land 2, the strip winding of magnetic and electrically conductivematerial is replaced by a conventional coil 15 formed of turns ofinsulated electrically conductive wire. Opposite ends of the wire arebrought out through the core to provide terminals to which a D. C.voltage may be applied.

In the modification illustrated in Fig. 3 the toroidal core structure 2is composed of a plurality of ring-like lamina containing thecircumferentially disposed saturating winding 10. This winding may be aconventional preformed coil as in Fig. 2 or as is preferred andillustrated the winding 10 is composed of wound strip or ribbon-likeconductor, the windings of which are insulated from each other and fromthe core structure as by means of the insulation 16. It is of coursepreferred in this ernbodiment that the ribbon-like conductors be formedof a magnetic material although such material may not possess theoptimum in electrical resistance. It is understood that the laminae 2may be held together in a conventional manner and that slots (not shown)are provided to receive the inner and outer ends of the spirally woundstrip coil 10. These slots are preferably formed by slitting thering-lamina and aligning the slits to form the Slots through whichproject the ends of the ribbon. It is understood also that theinductance coil 1 is wound about the core so that the ends of the ribbonare accessible through the main inductance coil. Clearly otherconstructions of the core may be devised, for example the laminated coremay be formed of ribbon windings in a manner similar to the inner coil,however, the construction illustrated is preferred. Also the ribbonconductor may be used alone as a core for the inductance winding.

It is apparent from the foregoing that there is provided by thisinvention an improved toroidal Winding the inducance of which may bevaried by altering the saturation of the closed core structure aboutwhich the toroid is wound with a ux produced by direct currentconductors contained within the core structure and wound in a directioncircumferentially of the core so that the saturating ux will be in adirection normal to the main flux.

Obviously many other modifications and variations of the presentinventionl are possible in the light of the above teachings. It istherefore to be understood, that, within the scope of the appendedclaim, this invention may be practiced otherwise than as specificallydescribed.

The invention herein described may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

I claim:

A variable reactance device comprising a multiturn spiral coil ofsubstantially ribbon-shaped high permeability conducting material,insulating means disposed between adjacent turns of said coil, a highpermeability nonconducting ferrite toroidally-shaped core having asubstantially continuous outside surface constructed of two symmetricalsolid sections with a continuous groove therein forming an annular spaceWithin the core body for receiving a high permeability coil, said spiralcoil being enclosed within said core with the conducting material ofsaid ribbon-shaped coil in direct Contact with said core, meanspenetrating said core for providing electrical con nections to theopposite ends of said spiral coil, and a toroidal coil of nonpermeableconducting material Wound around said score.

References Cited in the le of this patent UNITED STATES PATENTS 743,444Burgess et al Nov. 10, 1903 1,287,982 Hartley Dec. 17, 1918 1,289,418Elmen Dec. 31, 1918 1,561,782 Given Nov. 17, 1925 1,606,777 Payne Nov.16, 1926 1,935,208 Haydon Nov. 14, 1933 2,333,015 Kramer et al Oct. 26,1943 2,445,813 Walworth July 27, 1948 2,452,529 Snoek Oct. 26, 19482,474,988 Sargrove Iuly 5, 1949 OTHER REFERENCES Printed CircuitTechniques National Bureau of Standards Circular 468, issued November15, 1947. (Par- V ticularly page 18.)

